1. Field of the Invention
The present invention relates to a reversible ratcheting tool having a smaller head for convenient use in a limited space.
2. Description of the Related Art
U.S. Pat. No. 1,957,462 to Kress issued on May 8, 1934 discloses a ratchet wrench including a ratchet wheel 24 housed in a cylindrical recess 23 in the head 22. A pawl 25 is mounted in a second cylindrical recess 26 in the head 22 for controlling movement of the ratchet wheel 24. The pawl 25 is retained in place by a spring-biased plunger 41. Upon rotation of a thumb-piece 58 connected to the pawl 25, the pawl 25 is movable between two positions and thus provides driving and ratcheting of a socket in opposite directions. The pawl 25 is pivoted through a relatively long distance in the head 22, i.e., the head 22 must be relatively large to allow pivotal movement of the pawl 25. Furthermore, the pawl 25 engages with the teeth of the ratchet wheel 24 by only two teeth, i.e., the wrench is not capable of bearing high torque.
U.S. Pat. No. 4,328,720 to Shiel issued on May 11, 1982 discloses a socket wrench including a drive ring 30, a pawl 50 mounted in a recess 52 in the head 21 of the socket wrench and having two toothed portions 56 and 57, and an external latch handle 53 for controlling position of the pawl 50, thereby optionally causing a desired one of the toothed portions 56 and 57 to engage with a ratcheted outer peripheral portion 48 of the drive ring 30 and thus changing the ratcheting direction. Nevertheless, there are too many components in this socket wrench, and the head 21 is relatively large, as it has to receive the components. Processing and assembly for the components are both troublesome and time-consuming. In addition, transmission between the elements for changing the ratcheting direction is not reliable, as the latch handle 53 does not directly actuate the pawl 50. Furthermore, each toothed portion 56, 57 has only two teeth, i.e., the socket wrench is not capable of bearing high torque.
U.S. Pat. No. 5,626,062 to Colvin issued on May 6, 1997 discloses a ratchet wrench including a drive gear 48 mounted in a head 44 thereof. A reversing pawl 60 is mounted in the head 44 and has teeth 62 for engaging the drive teeth 50 of the drive gear 48 to provide driving and ratcheting of the socket 22 in opposite directions that are reversible by movement of the reversing pawl between two positions under control of a reversing lever 102. The reversing pawl 60 is pivoted through a relatively long distance in the head 44, i.e., the head must be large enough to allow pivotal movement of the reversing pawl 60. Furthermore, the pawl 60 engages with the teeth 50 of the drive gear 48 by only two teeth, i.e., the wrench is not capable of bearing high torque.
U.S. Pat. No. 4,762,033 to Chow issued on Aug. 9, 1988 discloses a ratchet wrench including a drive head 30 with inner ratchet teeth 42. A core assembly 34 is rotatably mounted in the drive head 30 and has a tool-coupling stud 56. Mounted in the core assembly 34 is a pawl 46 that engages with the teeth 42. Upon rotation of a control plate 60, the pawl 46 is movable between two positions and thus provides driving and ratcheting of a socket in opposite directions via transmission of an intercoupling, resilient, spring-like wire 104 that is mounted in the core assembly. The pawl 46 engages with the teeth 42 by about five teeth and thus may bear higher torque. Nevertheless, the user must use both hands to switch the ratcheting direction. In addition, there are too many components in this wrench, and the head must be relatively large for receiving the components and allowing movement of the pawl 46. Processing and assembly for these components are both troublesome and time-consuming. Furthermore, the wire 104 tends to malfunction as a result of fatigue and thus fails to provide the required switching direction.
U.S. Pat. No. 4,520,697 to Moetteli issued on Jun. 4, 1985 discloses a ratchet wrench including a holed head 22xe2x80x2 having inner ratchet teeth 30xe2x80x2. Mounted in the head 22xe2x80x2 is a drive member 32xe2x80x2 with a hexagonal drive portion 36xe2x80x2. Also mounted in the head 22xe2x80x2 is a pawl 54xe2x80x2 having a first set of ratchet teeth 58xe2x80x2 and a second set of ratchet teeth 60xe2x80x2 for selectively engaging with the teeth 30xe2x80x2. A reverser plate 70xe2x80x2 is mounted on top of the drive member 32xe2x80x2 and includes two reverser pins 74xe2x80x2 for connection with the pawl 54xe2x80x2. The ratcheting action is reversible by merely moving the reverser pins 74xe2x80x2. Nevertheless, there are too many components in this wrench, and the head is large, as it has to receive the components. In addition, processing and assembly are both troublesome and time-consuming. Furthermore, the pawl 54xe2x80x2 engages with the teeth 30xe2x80x2 by only two teeth, i.e., the wrench is not capable of bearing high torque.
U.S. Pat. No. 3,337,014 to Sandrick issued on Aug. 22, 1967 discloses a ratchet wrench including a head 10 provided with internal periphery ratchet teeth 15. Mounted in the head 10 is a double-ended pawl 26 that is pivotable by a spring pressed plunger 38. Upon rotation of a finger piece 36, the pawl 26 is movable between two positions and thus provides driving and ratcheting of a socket in opposite directions. Nevertheless, there are too many components in this wrench, and the head is large, as it has to receive the components. In addition, processing and assembly are both troublesome and time-consuming. The pawl 26 engages with the teeth 15 by only three teeth, i.e., the wrench is not capable of bearing high torque. Furthermore, the user must use both hands to switch the ratcheting direction.
U.S. Pat. No. 5,144,869 to Chow issued on Sep. 8, 1992 discloses a ratchet wrench including a handle with two box ends each having a ratchet wheel 12 mounted therein. A pawl 20 is engaged with each ratchet wheel 12. A knob 30 is mounted in a middle of the handle and receives a disc 40 that is connected to each pawl 20 by two resilient members 26. When the knob 30 and the disc 40 are rotated, the first toothed section 22 and the second toothed section 23 of each pawl 20 are caused to engage with the associated ratchet wheel 12 via transmission by the resilient members 26, thereby controlling the torque transmission direction of the ratchet wheel 12. Nevertheless, the resilient plates 26 tend to malfunction as a result of fatigue. In addition, position of each pawl 25 cannot be precisely controlled. The handle structure is weak, as it must be machined to provide a space for receiving the knob 30, the resilient members 26, and the pawls 25. Furthermore, each pawl 25 engages with the ratchet wheel 12 by only two teeth, i.e., the wrench is not capable of bearing high torque.
FIG. 11 of the drawings illustrates a conventional ratcheting tool including a head 11xe2x80x2 having a first compartment 121xe2x80x2 for receiving a drive member 20xe2x80x2 with a ratchet wheel 21xe2x80x2, a second compartment 122xe2x80x2 for receiving a pawl 30xe2x80x2, and a third compartment 123xe2x80x2 for receiving a switch block 40xe2x80x2. The pawl 30xe2x80x2 includes teeth 31 xe2x80x2 formed on a first side thereofxe2x80x2 for engaging with teeth of the ratchet wheel 21xe2x80x2. The switch block 40xe2x80x2 includes a first side having two operative sections 416xe2x80x2 for selectively bearing against a second side of the pawl 30xe2x80x2. A second side of the switch block 40xe2x80x2 includes two arcuate grooves 414xe2x80x2. A thumb piece 42xe2x80x2 includes a stem 421xe2x80x2 that extends through a hole 13xe2x80x2 in the head 11xe2x80x2, a vertical hole 413xe2x80x2 in the switch block 40xe2x80x2, and a hole 71xe2x80x2 of a cover 70xe2x80x2. A spring 61 xe2x80x2 is mounted in a cavity 14xe2x80x2 in the web area of the tool for urging a ball 62xe2x80x2 to engage with one of the grooves 414xe2x80x2. An elastic ring 50xe2x80x2 is wound around a stub 411xe2x80x2 on the switch block 40xe2x80x2 and includes an engaging end 51xe2x80x2 engaged in a hole 32xe2x80x2 of the pawl 30xe2x80x2. Upon rotation of the thumb piece 42xe2x80x2, the pawl 30xe2x80x2 is movable between two positions and thus provides driving and ratcheting of a socket in opposite directions via transmission of the switch block 40xe2x80x2 and the elastic a ring 50xe2x80x2. The pawl 30xe2x80x2 engages with the ratchet wheel teeth by more teeth and thus may bear higher torque. Nevertheless, the pawl 30xe2x80x2 has a long travel in the head 11 xe2x80x2, and the head 11xe2x80x2 must be relatively large for receiving the ratchet wheel 21xe2x80x2, the pawl 30xe2x80x2, and the switch block 40xe2x80x2 and allowing pivotal movement of the pawl 30xe2x80x2 and the switch block 40xe2x80x2. In addition, the elastic ring 50xe2x80x2 is required for transmitting the force from the switch block 40xe2x80x2 to the pawl 30xe2x80x2 so as to change the ratcheting direction. More specifically, position of the pawl 30xe2x80x2 cannot be precisely controlled. In addition, the elastic ring 50xe2x80x2 tends to malfunction as a result of fatigue.
In conclusion, the above-mentioned conventional ratcheting tools fail to provide high torque operation, as most of the pawls merely engage with the ratchet wheel by at best three or five teeth. The head of the ratcheting tool has to be relatively large for accommodating those components and thus is difficult to be used in a limited space. In addition, the pawl is directly driven by the switch button or reverser plate or like element such that the pawl tends to be disengaged from the ratchet wheel or like element if the switch block is inadvertently impinged. Generally, a skilled user uses a combination wrench, a spanner with two open ends, or a ring spanner for tightening or loosening a fastener in a limited space. Yet, it is found that free rotation of the ratcheting tool during ratcheting is too large (larger than the theoretic value of 5xc2x0), as the pawl has a long travel.
FIGS. 12 and 13 illustrate another conventional ratcheting tool 100xe2x80x2 including a head having a compartment 101xe2x80x2 for receiving a drive member with a ratchet wheel 108xe2x80x2. The pawl 102xe2x80x2 includes teeth 103xe2x80x2 formed on a side thereofxe2x80x2 for engaging with teeth of the ratchet wheel 108xe2x80x2. A switch block 104xe2x80x2 is attached to the pawl 102xe2x80x2 via an elastic member 106xe2x80x2 and includes a thumb piece 105xe2x80x2. Upon pivotal movement of the thumb piece 105xe2x80x2, the pawl 102xe2x80x2 is movable between two positions and thus provides driving and ratcheting for a socket in opposite directions via transmission of the pawl 102xe2x80x2 and the ratchet wheel 108xe2x80x2. The pawl 102xe2x80x2 engages with the ratchet wheel teeth by more teeth and thus may bear higher torque. Nevertheless, pivotal axis for the switch block 104xe2x80x2 is not coincident with rotational axis of the ratchet wheel 108xe2x80x2. Namely, the head of the ratcheting tool must be machined to form additional grooves or compartments 107xe2x80x2 and 109xe2x80x2 (FIG. 12) for accommodating the pawl 102xe2x80x2 and the switch block 104xe2x80x2. As a result, the head of the ratcheting tool is relatively large. In addition, the pawl 102xe2x80x2 tends to be disengaged from the ratchet wheel if the thumb piece 105xe2x80x2 is inadvertently impinged. Thus, the engagement between the pawl 102xe2x80x2 and the ratchet wheel 108xe2x80x2 is adversely affected.
It is a primary object of the present invention to provide a reversible ratcheting tool with a small head while providing improved driving torque for convenient use in a limited space.
A ratcheting tool in accordance with the invention comprises:
a handle;
a head extended from the handle and having a compartment therein;
a drive member including a first end, a second end, and a gear wheel formed between the first end and the second end, the gear wheel being rotatably mounted in the compartment and including an outer periphery with a plurality of first teeth, the first end of the drive member including an engaging groove;
a pawl mounted in the compartment and including a first side with a plurality of second teeth facing the first teeth of the gear wheel and a second side facing away from the gear wheel, the pawl comprising an upper end;
a reversing plate mounted to the first end of the drive member and pivotable about a rotational axis of the gear wheel between a first position and a second position, the reversing plate comprising a retainer block engaged with the upper end of the pawl for moving the pawl between a first ratcheting position and a second ratcheting position, wherein the second teeth of the pawl is engaged with the first teeth of the gear wheel for ratcheting in a first direction when the pawl is in the first ratcheting position, and wherein the second teeth of the pawl is engaged with the first teeth of the gear wheel for ratcheting in a second direction opposite to the first ratcheting direction when the pawl is in the second ratcheting position, the reversing plate further comprising a positioning piece for engaging with the engaging groove of the upper end of the drive member to thereby prevent disengagement of the reversing plate from the drive member while allowing rotational movement of the reversing plate relative to the drive member, and
means for retaining the reversing plate in one of the first position and the second position.
Other objects, advantages, and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.